Mac Pro Dual-Core Intel Xeon/Snow Leopard (10A432)/Parallels 4.0.3846

I am running Windows 7 Ultimate Evaluation copy Build 7100 in 64-bit OS. I am trying to install Microsoft Windows 7 Ultimate x64 Multilanguage. But when I double-click the setup.exe, I got this error:
"The version of this file is not compatible… Check your computer’s system information to see whether you need an x86 (32-bit) or x64 (64-bit) version of the program…"
But Control Panel > System and Security > System > System type: 64-bit Operating System

So how come I can't run the 64-bit setup.exe?